The present invention relates to a plasma processing apparatus and a plasma processing method.
A plasma etching apparatus is utilized during the process of manufacturing a semiconductor device in the prior art. In the processing chamber of the apparatus, an upper electrode and a lower electrode are set facing opposite each other. In the plasma etching apparatus adopting this structure, the processing gas introduced into the processing chamber is raised to plasma when high-frequency power is applied to the lower electrode and the workpiece placed on the lower electrode, such as a semiconductor wafer (hereafter referred to as a xe2x80x9cwaferxe2x80x9d) becomes etched. In addition, the lower electrode is internally provided with a temperature control mechanism to adjust the wafer temperature. The lower electrode is also provided with a ring body. The ring body is constituted of an inner ring body and an outer ring body. The inner ring body is set so as to encompass the outer edges of the wafer placed on the lower electrode. The outer ring body is set so as to encompass the periphery of the inner ring body.
The inner ring body is constituted of a conductive material. Thus, the external diameter of the wafer can be made to appear electrically large relative to the plasma during the plasma processing. As a result, the plasma is admitted to the entire wafer in an even manner including the outer edges of the wafer as well as the central area. The outer ring body is constituted of an insulating material. Thus, the plasma becomes concentrated on the wafer during the plasma processing so that the plasma can be evenly guided over the entire wafer surface.
However, the conductive inner ring body where intense ion collisions occur, as at the wafer, becomes heated very easily. In addition, the inner ring body is set above the lower electrode unlike the outer ring body which is directly secured to the lower electrode. As a result, since the heat of the inner ring body cannot be fully radiated to the lower electrode in the pressure reduced atmosphere during the processing, the temperature of the inner ring body becomes high. This results in an inconsistent radical concentration in the vicinity of the inner ring body, to reduce the etching rate at the outer edges of the wafer adjacent to the inner ring body. In addition, a discrepancy in the processing is created between the center of the wafer and the outer edges of the wafer and it becomes difficult to achieve uniform processing over the entire wafer surface.
Technologies for processing wafers having a large diameter, e.g., 300 mm, have been proposed in recent years. The processing area at the outer edges of the wafer increases in proportion to the diameter of the wafer. Consequently, the reduction in yield is further exacerbated unless uniform processing is achieved at the outer edges of the wafer, as described above. In addition, in order to improve the productivity of semiconductor element manufacturing, it is necessary to form elements as close to the outer edges of the wafer as possible. However, this technical requirement cannot be satisfied unless uniform processing is achieved at the outer edges of the wafer.
Furthermore, the rate at which ions in the plasma collide with each other at the insulating outer ring body is a lower than the collision rate at the inner ring body. Thus, the temperature of the outer ring body rises more slowly than the temperature at the inner ring body. As a result, when performing continuous processing, the temperature at the outer ring body in particular, is not stable, after the start of processing until a specific number of wafers have been processed. If the temperature at the outer ring body is unstable, the radical concentration at the periphery of the outer ring body, e.g., at the area encompassing the outer edges of the wafer, becomes inconsistent. Consequently, uniform processing is not achieved at the center of the wafer and at the outer edges of the wafer, resulting in difficulty in performing uniform processing over the entire wafer surface. This necessitates processing to be performed on a specific number of dummy wafers until the temperature of the outer ring body becomes stabilized. Thus, the throughput is reduced.
The present invention has been completed by addressing the problems of the prior art discussed above. A first object of the present invention is to provide a new and improved plasma processing apparatus capable of performing uniform processing over the entire surface of a workpiece by generating radicals evenly over the workpiece and the outer edges of the workpiece and a method adopted in this plasma processing apparatus.
A second object of the present invention is to provide a new and improved plasma processing apparatus capable of performing consistent and stable processing on a workpiece immediately after the start of processing and a method adopted in this plasma processing apparatus.
In order to achieve the objects described above, in a first aspect of the present invention, a plasma processing apparatus that performs plasma processing on a workpiece placed on an electrode provided inside a processing chamber comprising a means for temperature control provided at the electrode, a conductive ring body encompassing the periphery of the workpiece placed on the electrode, a first gas supply passage through which a heat transfer gas is supplied to the space between the conductive ring body and the electrode, a means for pressure regulation that regulates the pressure of the heat transfer gas that is supplied so that the temperature of the conductive ring body and the temperature of the workpiece are set roughly equal to each other and a first means for control that controls the means for pressure regulation, is provided.
In this structure, the first means for control adjusts the means for pressure regulation to set the pressure of the heat transfer gas to a specific level. The heat transfer gas, having undergone this adjustment, is then supplied to the space between the conductive ring body and the electrode via the first gas supply passage. The heat transfer gas supplied in this manner increases the thermal conductivity between the conductive ring body and the electrode even in the pressure reduced atmosphere during the processing so that the heat of the conductive ring body can be reliably absorbed by the electrode. Thus, even if the conductive ring body is heated, the temperature of the conductive ring body can be maintained at a specific level. As a result, consistency is achieved in the radical concentration in the vicinity of the outer edges of the workpiece adjacent to the conductive ring body to enable a specific type of processing to be performed at the outer edges of the workpiece. In addition, the pressure of the heat transfer gas can be adjusted as necessary by the means for gas pressure regulation. Consequently, the temperature of the conductive ring body can be set as appropriate for a specific process to be implemented. The means for pressure regulation is controlled so as to roughly equalize the temperature of the conductive ring body with the temperature of the workpiece. This structure achieves consistency in the concentration of radicals distributed around the workpiece and the conductive ring body. As a result, uniform processing is achieved at the center of the workpiece and at the outer edges of the workpiece to realize uniform processing over the entire surface of the workpiece.
Furthermore, it is desirable that the first means for control implement control on the means for pressure regulation based upon temperature information obtained through detection performed by temperature sensors that measure the temperature of the conductive ring body and the temperature of the workpiece. By adopting this structure, the temperature of the conductive ring body can be set at a specific level in conformance to the temperature of the workpiece, which changes continually during the processing.
In addition, one or a plurality of second gas supply passages may be provided at the electrode separately from and independently of the first gas supply passage, through which a heat transfer gas is supplied to the space between the workpiece and the electrode. By adopting this structure, in which the first gas supply passage and the second gas supply passage are formed separately from and independently of each other, the types and supply pressures of the heat transfer gases to be supplied to the space between the workpiece and the electrode and to the space between the conductive ring body and the electrode can be individually selected. The thermal conductivity between the workpiece and the electrode and the thermal conductivity between the conductive ring body and the electrode can be set independently of each other to assure reliable temperature control in the conductive ring body.
The plasma processing apparatus may be further provided with an insulating ring body surrounding the periphery of the conductive ring body, a means for heat application located at the insulating ring body and a second means for control that controls the means for heat application. In this structure, the second means for control implements control on the means for heat application so that the insulating ring body can be heated to a specific temperature in advance before starting the processing. As a result, any changes in the temperature of the insulating ring body that would otherwise occur during the processing are essentially eliminated to allow a specific type of processing to be performed on the workpiece even immediately after the start of processing. Thus, since it is not necessary to stabilize the temperature of the insulating ring body by performing preliminary processing on dummy workpieces, an improvement in throughput is achieved. In addition, since the temperature of the insulating ring body can be controlled as appropriate, the temperature of the insulating ring body can be maintained at a specific level before and after the processing as well as during the processing.
In a second aspect of the present invention, a plasma processing apparatus that performs plasma processing on a workpiece placed on an electrode provided inside a processing chamber, comprising a means for temperature control provided at the electrode, a conductive ring body encompassing the periphery of the workpiece placed on the electrode, a first gas supply passage through which a heat transfer gas is supplied to the space between the conductive ring body and the electrode, a second gas supply passage communicating with the first gas supply passage, through which a heat transfer gas is supplied to the space between the workpiece and the electrode, a means for pressure regulation that regulates the pressure of the heat transfer gas being supplied and a means for control that controls the means for pressure regulation is provided.
By adopting this structure, in which the first gas supply passage and the second gas supply passage are made to communicate with each other, the heat transfer gas can be supplied to the space between the conductive ring body and the electrode without having to connect a gas supply system that is separate and independent of the first gas supply passage. As a result, the structure of the apparatus is simplified. In addition, by adopting the structure described above, which can be achieved without having to greatly modify the apparatus in the prior art described earlier, the present invention can be implemented easily.
In a third aspect of the present invention, a plasma processing apparatus that performs plasma processing on a workpiece placed on an electrode provided inside a processing chamber comprising a means for temperature control provided at the electrode, a conductive ring body encompassing the periphery of the workpiece placed on the electrode, a first gas supply passage through which a heat transfer gas is supplied to the space between the conductive ring body and the electrode, a second gas supply passage through which a heat transfer gas at a first pressure level is supplied to the space between the workpiece and the electrode, a third gas supply passage through which a heat transfer gas at a second pressure level is supplied to the space between the workpiece and the electrode, a first link passage for linking the first gas supply passage and the second gas supply passage that can be opened/closed freely, a second link passage for linking the first gas supply passage and the third gas supply passage that can be opened/closed freely and a means for control that controls the length of time over which the first link passage remains open and the length of time over which the second link passage remains open to set the temperature of the conductive ring body and the temperature of the workpiece roughly equal to each other is provided.
In this structure, the heat transfer gas at the first pressure level is supplied to the first gas supply passage while the first link passage is open. In addition, the heat transfer gas at the second pressure level is supplied to the first gas supply passage while the second link passage is open. The lengths of time over which the first and second link passages remain open are controlled as appropriate by the means for control. As a result, the temperatures of the workpiece and the conductive ring body can be set roughly equal to each other without having to connect a separate and independent gas supply system to the first gas supply passage.
In a fourth aspect of the present invention, a plasma processing apparatus that performs plasma processing on a workpiece placed on an electrostatic chuck formed on a mounting surface of an electrode provided inside a processing chamber comprising a means for temperature control provided at the electrode, a conductive ring body encompassing the periphery of the workpiece placed on the electrostatic chuck and a thermal conductivity adjusting member provided between the electrode and the conductive ring body to set the thermal conductivity between the electrode and the conductive ring body and the thermal conductivity between the electrode and the workpiece roughly equal to each other is provided.
In this structure, the thermal conductivity adjusting member is provided between the conductive ring body and the electrode. Thus, almost uniform thermal conductivity is achieved between the workpiece and the electrode and between the conductive ring body and the electrode. As a result, the temperature of the conductive ring body and the temperature of the workpiece can be essentially matched through a relatively simple structure. In addition, the structure can be easily realized simply by providing the thermal conductivity adjusting member between the conductive ring body and the electrode. Furthermore, the increase in the cost of manufacturing the processing apparatus can be minimized.
In a fifth aspect of the present invention, a plasma processing apparatus that performs plasma processing on a workpiece placed on an electrode provided inside a processing chamber comprising a means for temperature control provided at the electrode, a conductive ring body encompassing the periphery of the workpiece placed on the electrode and a means for pressure application that applies a pressure to the conductive ring body toward the electrode and is capable of adjusting the level of the pressure applied to the conductive ring body, is provided.
By adopting this structure, the conductive ring body can be placed in complete contact with the electrode by the means for pressure application. As a result, the thermal conductivity between the conductive ring body and the electrode is improved so that the heat of the conductive ring body can be absorbed by the electrode. In addition, the means for pressure application is capable of adjusting the level of the pressure applied to the conductive ring body. Thus, the temperature of the conductive ring body can be set at a specific level as appropriate. Furthermore, since the conductive ring body only needs to be pressed against the electrode by the means for pressure application, simplification in the structure of the apparatus is achieved.
In a sixth aspect of the present invention, a plasma processing method for performing plasma processing on a workpiece placed on an electrode provided inside a processing chamber, comprising a step in which a means for temperature control provided at the electrode is adjusted to set the temperature of the electrode to a specific level, a step in which a heat transfer gas is supplied to the space between a conductive ring body encompassing the periphery of the workpiece placed on the electrode and the electrode and a step in which the pressure level of the heat transfer gas being supplied is regulated so as to set the temperature of the workpiece and the temperature of the conductive ring body roughly equal to each other is provided.
In this method, the temperature of the conductive ring body can be controlled by supplying the heat transfer gas at a specific supply pressure to the space between the conductive ring body and the electrode so as to set the temperature of the workpiece and the temperature of the conductive ring body roughly equal to each other. As a result, the thermal conductivity between the conductive ring body and the electrode can be increased. In addition, by regulating the level of the supply pressure of the heat transfer gas, the temperature of the conductive ring body can be adjusted as appropriate. During this process, it is desirable that the supply pressure of the heat transfer gas be controlled based upon temperature information obtained by measuring the temperature of the conductive ring body and the temperature of the workpiece. By adopting such a method, the temperature of the conductive ring body can be matched with the temperature of the workpiece which changes continuously during the processing. Furthermore, a high degree of consistency in the concentration of radicals distributed around the workpiece and the conductive ring body is achieved. Consequently, no discrepancy in the processing occurs between the center of the workpiece and the outer edges of the workpiece, to realize uniform processing over the entire surface of the workpiece.
It is desirable to implement an additional step in which heat is applied to an insulating ring body encompassing the periphery of the conductive ring body to maintain the temperature of the insulating ring body at a constant level during plasma processing performed on the workpiece. This maintains the temperature of the insulating ring body at a specific level before the start of processing. As a result, stable processing can be performed on the workpiece even immediately after the processing starts.
In a seventh aspect of the present invention, a plasma processing method for performing plasma processing on a workpiece placed on an electrode provided inside a processing chamber characterized in that the plasma processing is performed by setting the temperature of the workpiece, which is controlled by a means for temperature control provided at the electrode and the temperature of a conductive ring body encompassing the periphery of the workpiece set on the electrode roughly equal to each other is provided.
In this method, the plasma processing is performed on the workpiece in a state in which the temperature of the workpiece, which is controlled at a specific level, and the temperature of the conductive ring body are practically matched. It is to be noted that the temperature of the workpiece and the temperature of the conductive ring body may be set roughly equal to each other by supplying a heat transfer gas into the space between the conductive ring body and the electrode, by providing a thermal conductivity adjusting member or by pressing the conductive ring body against the electrode as explained earlier in reference to the preceding aspects of the present invention.
In addition, it is desirable to apply heat to an insulating ring body encompassing the periphery of the conductive ring body to maintain it at a constant temperature level. Since this will maintain the temperature of the insulating ring body virtually unchanged, uniform processing is achieved.